1. Technical Field
This invention relates generally to ion generators and ion wind devices, and more specifically to an improved method and apparatus for reducing the production of ozone in ion wind devices.
2. Background Art
Ion wind devices such as described in Lee U.S. Pat. No. 4,789,801 (incorporated herein by reference) provide accelerated gas ions generated by the use of differential high voltage electric fields between an array of one or more emitters and a plurality of collectors (accelerators). The ions are entrained in the ambient bulk gases, causing the gases to flow. Gas velocities can reach as high as eight hundred feet per minute. However, the high voltage electric fields used to generate the gas ions and provide the force necessary for gas acceleration are also responsible for creating molecular dissociation reactions, the most common of which include ozone generated from oxygen when such devices are operating in a breathable atmosphere. It is an object of this invention to provide methods to reduce the production of ozone in such devices.
The U.S. Food and Drug Administration has determined that indoor airborne ozone in concentrations above 50 ppb (parts per billion) may be hazardous to humans. NIOSH has ruled that indoor concentrations of ozone above 100 ppb may be hazardous to humans. Devices which utilize high voltage electric fields to generate atmospheric plasma, corona discharge and air ions are all susceptible to generating the allotrope, ozone. There exists a linear relationship between the level of the high voltage fields and current and the level of ozone concentration in most direct current operated ion wind systems. Also, a linear relationship exists between the acceleration velocity and intensity of the electric fields. Typically the higher the voltage the higher the acceleration. Since it is desired to have maximum acceleration, methods must be employed to limit or eliminate unwanted ozone production.